WASHINGTON – The U.S. Army Corps of Engineers has uncovered what could be a fourth major disposal area for World War I-era munitions and chemical weapons in the nation’s capital.

Digging was suspended April 8 as a precaution at the site in the pricey Spring Valley neighborhood near American University after workers pulled smoking glassware from the pit, project manager Dan Noble said Thursday.

Preliminary tests show the glassware was contaminated with the toxic chemical arsenic trichloride. Officials will review safety procedures before digging continues.

Workers also discovered a jar about three-quarters full of a dark liquid that turned out to be the chemical agent mustard. It was used during World War I as a weapon that caused blisters, breathing problems and vomiting.